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  • <img alt="FeCr_{2}O_{4}+Na_{2}CO_{3}+O_{2}\overset{fusion}{\rightarrow}[X]\xrightarrow[H^{+}]{H_{2}O} [Y]\xrightarrow[H^{+}]{H_{2}O}[Z]" src="https://learn.careers360.com/latex-image/?FeCr_%7B2%7DO

FeCr_{2}O_{4}+Na_{2}CO_{3}+O_{2}\overset{fusion}{\rightarrow}[X]\xrightarrow[H^{+}]{H_{2}O} [Y]\xrightarrow[H^{+}]{H_{2}O}[Z]

Which of the following statements are true for compounds [X], [Y] and [Z] ?

Option: 1

In all three compounds, the chromium is in +6 oxidation state.


Option: 2

[Z] is a deep-blue violet coloured compound which decomposes rapidly in aqueous solution into Cr+3 and dioxygen


Option: 3

Saturated solution of [Y] gives bright orange compound, chromic anhydride, with conc.H_{2}SO_{4}


Option: 4

All of the above

 


Answers (1)

best_answer

 

Test of Chromium(3+) -

Cr(OH)_3  is oxidised to CrO^{2-}_4 in presence of NaOH & H_2O_2

2Cr(OH)_3 + H_2O_2 +4OH^{-}\rightarrow 2CrO^{2-}_4 + 8H_2O

CrO^{2-}_4gives yellow ppt with Pb^{2+}

Pb^{2+} +CrO^{2-}_4 \rightarrow PbCrO_4 Yellow

CrO^{2-}_4 in acidic medium with H_2O_2 \: gives\: CrO_5 \: (Blue)

CrO^{2-}_4 +2H^{+} + 2H_2O_2 \rightarrow CrO_5(Blue) +3H_2O_2 \:

- wherein

Yellow PbCrO_4 \: and \: blue \: CrO_3\:confirmed \:the \:presence \:of\:Cr^{3+}

 

 

 

4FeCr_{2}O_{4}+8Na_{2}CO_{3}+7O_{2}\overset{fusion}{\rightarrow}Na_{2}CrO_{4}\xrightarrow[H^{+}]{H_{2}O} Na_{2}Cr_{2}O_{7}\xrightarrow[H^{+}]{H_{2}O}CrO(O_{2})_2

deep blue violet \overset{H_{2}O}{\rightarrow}O_{2}+H_{2}O+Cr^{+3}

Na_{2}Cr_{2}O_{7}+H_{2}SO_{4}\rightarrow 2CrO_{3} (chromic anhydride) +Na_{2}SO_{4}+H_{2}O

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shivangi.shekhar

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